Intrinsic neurons of the central nervous system (CNS) do not successfully regenerate following trauma. The lack of regeneration accounts, in part, for the poor prognosis of patients who have sustained serious injury to the spinal cord or brain. The isolation of molecules that enhance neuronal survival and facilitate process outgrowth could significantly improve a patient's response and outlook following CNS injury. This proposal is based on our unique finding that a protein mitogen, basic fibroblast growth factor (bFGF), enhances survival and neurite extension from CNS neurons in vitro. Nerve growth factor is the only other (Homogeneous) trophic molecule reported to affect CNS neurons, but its action in the CNS is restricted to a small population of cells in the basal forebrain. In order to exploit bFGF as a potential therapeutic agent it is necessary to know more about its basic biology, including the types of neurons that respond to it and the mechanism by which it works. Therefore, we plan to survey defined regions of the CNS for the presence of neurons responsive to bFGF by utilizing primary cell culture techniques. Neurons will be identified using immunocytochemical techniques employing antibodies to defined neuronal antigens. The cells will be further characterzied and classified according to subtype by analyzing their expression of neurotransmitters and neuropeptides using immunocytochemical methods. Upon characterization of the neuronal cultures we will begin to analyze the mechanism of bFGF action by studying its receptor. Receptor binding is the first step in initiating the action of most polypeptide hormones. An 125I-bFGF tracer will be developed and used for demonstrating and identifying the bFGF receptor on neurons and neurolgia. Molecular characterization will be performed on solubilized receptors using SDS polyacrylamide-gel electrophoresis of receptor covalently attached to tracer by chemical cross-linking. We will correlate the response of neuronal populations in vitro with receptor expression in vivo by combining the 125I-bFGF tracer with frozen sections of rat brain. In this manner the ontogeny and distribution of bFGF receptors in the CNS will be accurately mapped.